Novel Constraint on Parameter Space of the Georgi-Machacek Model by Current LHC Data

TL;DR

This paper uses current LHC data on same-sign diboson production to set new constraints on the parameter space of the Georgi-Machacek model, particularly on triplet VEVs and Higgs masses, and explores future discovery prospects.

Contribution

It provides the first direct experimental constraints on the Georgi-Machacek model using LHC diboson data, focusing on the effects of new Higgs bosons on gauge boson vertices.

Findings

Current 8-TeV data exclude certain triplet VEVs and Higgs masses.

Predicted 14-TeV LHC data could discover or further constrain the model.

The model's parameter space is significantly limited by existing measurements.

Abstract

The same-sign diboson process $pp\to W^\pm W^\pm jj$ has been measured at the LHC using leptonic decay channels of the $W$ bosons, with production cross sections of two fiducial regions reported to be consistent with the standard model expectations within 1 sigma. These results constrain new physics models with a modified $W^+W^+W^-W^-$ vertex. We consider in particular the Georgi-Machacek model in which the quartic $W$ boson vertex is effectively modified due to mediations of new Higgs bosons in the model. The relevant gauge-gauge-scalar couplings are all proportional to the vacuum expectation value of the isospin triplets, which can be of $\mathcal{O}(10)$ GeV because of custodial vacuum alignment. Using the current 8-TeV data at the LHC, we exclude parameter space on the plane of the triplet vacuum expectation value and the new Higgs boson mass. The expected discovery reach at the 14-TeV LHC is also studied.